1. Field of the Invention
The present invention relates to a lens-fitted photo film unit. More particularly, the present invention relates to a lens-fitted photo film unit having a simple mechanism for changing over exposure.
2. Description Related to the Prior Art
There is a lens-fitted photo film unit which is pre-loaded with photo film as a single-use camera sold at a low cost, and with which a photograph can be taken with high image quality without further difficulty than depression of a shutter. The lens-fitted photo film unit has a fixed aperture. This possibility of the high image quality is based firstly on high speed of the photo film as pre-loaded, and secondly on fine adjustment of exposure in printing operation in a photo laboratory. In producing a photographic print from the photo film, an exposure amount for exposing photographic paper can be sufficiently corrected by compensation in the printing, even if the exposure amount has not been optimum initially.
The high speed photo film can be advantageously used, because a shutter speed can be raised and an aperture stop can be rendered small. The high shutter speed is effective in reducing the influence of a camera shake which would be caused incidentally by manual operation. The small aperture stop is effective in refining pan-focus performance.
In use of the high speed photo film, it is likely to photograph over-exposed frames, typically outdoors under sun-light even within the range of the latitude of the photo film. It is necessary to print an over-exposed frame for a long exposure time for the purpose of optimizing exposure of photographic paper.
A user of the lens-fitted photo film unit deposits it to a photofinisher, which is expected to effect operation of developing the photo film and printing photographs quickly. However the printing operation requires longer time if there are a greater number of over-exposed frames. This is inconsistent with efficiency.